kasan, page_alloc: rework kasan_unpoison_pages call site

Rework the checks around kasan_unpoison_pages() call in post_alloc_hook().

The logical condition for calling this function is:

 - If a software KASAN mode is enabled, we need to mark shadow memory.

 - Otherwise, HW_TAGS KASAN is enabled, and it only makes sense to set
   tags if they haven't already been cleared by tag_clear_highpage(),
   which is indicated by init_tags.

This patch concludes the changes for post_alloc_hook().

Link: https://lkml.kernel.org/r/0ecebd0d7ccd79150e3620ea4185a32d3dfe912f.1643047180.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Acked-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Collingbourne <pcc@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 386898f1a7c396681ac0a5e9f6c045ad18e2d234..350bb27dc4bb61de31e034ef73833ca3e3d5d63e 100644 (file)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2382,15 +2382,20 @@ inline void post_alloc_hook(struct page *page, unsigned int order,
                /* Note that memory is already initialized by the loop above. */
                init = false;
        }
-       if (kasan_has_integrated_init()) {
-               if (!init_tags) {
-                       kasan_unpoison_pages(page, order, init);
+       /*
+        * If either a software KASAN mode is enabled, or,
+        * in the case of hardware tag-based KASAN,
+        * if memory tags have not been cleared via tag_clear_highpage().
+        */
+       if (IS_ENABLED(CONFIG_KASAN_GENERIC) ||
+           IS_ENABLED(CONFIG_KASAN_SW_TAGS) ||
+           kasan_hw_tags_enabled() && !init_tags) {
+               /* Mark shadow memory or set memory tags. */
+               kasan_unpoison_pages(page, order, init);
 
-                       /* Note that memory is already initialized by KASAN. */
+               /* Note that memory is already initialized by KASAN. */
+               if (kasan_has_integrated_init())
                        init = false;
-               }
-       } else {
-               kasan_unpoison_pages(page, order, init);
        }
        /* If memory is still not initialized, do it now. */
        if (init)